#include "bootpack.h"

struct TASKCTL *taskctl;
struct TIMER *task_timer;

struct TASK *task_now(void)
{
    struct TASKLEVEL *tl = &taskctl->level[taskctl->now_lv];
    return tl->tasks[tl->now];
}

void task_add(struct TASK *task)
{
    struct TASKLEVEL *tl = &taskctl->level[task->level];
    tl->tasks[tl->running] = task;
    tl->running++;
    task->flag = TASK_RUNNING;
    return;
}

void task_remove(struct TASK *task)
{
    int i;
    struct TASKLEVEL *tl = &taskctl->level[task->level];

    /* search task */
    for (i = 0; i < tl->running; i++)
    {
        if (tl->tasks[i] == task)
            break;
    }
    
    tl->running--;
    if (i < tl->now)
        tl->now--;
    if (tl->now >= tl->running)
        tl->now = 0;
    task->flag = TASK_SLEEPING;

    /* 移动 */
    for (; i < tl->running; i++)
        tl->tasks[i] = tl->tasks[i + 1];

    return;
}

void task_switchsub(void)
{
    int i;
    /* 寻找最高LEVEL */
    for (i = 0; i < MAX_TASKLEVELS; i++)
    {
        if (taskctl->level[i].running > 0)
            break;
    }
    taskctl->now_lv = i;
    taskctl->lv_change = 0;
    return;
}

void task_idle(void)
{
    while (1)
        io_hlt();
}

struct TASK *task_init(struct MEMMAN *memman)
{
    struct TASK *task, *idle;
    struct SEGMENT_DESCRIPTOR *gdt = (struct SEGMENT_DESCRIPTOR *) ADR_GDT;
    taskctl = (struct TASKCTL *) memman_alloc_4k(memman, sizeof(struct TASKCTL));
    for (int i = 0; i < MAX_TASKS; i++)
    {
        taskctl->tasks[i].flag = 0;
        taskctl->tasks[i].sel = (TASK_GDT + i) * 8;
        taskctl->tasks[i].tss.ldtr = (TASK_GDT + MAX_TASKS + i) * 8;
        set_segmdesc(gdt + TASK_GDT + i, 103, (int) &taskctl->tasks[i].tss, AR_TSS32);
        set_segmdesc(gdt + TASK_GDT + MAX_TASKS + i, 15, (int) &taskctl->tasks[i].ldt, AR_LDT);
    }
    for (int i = 0; i < MAX_TASKLEVELS; i++)
    {
        taskctl->level[i].running = 0;
        taskctl->level[i].now = 0;
    }

    task = task_alloc();
    task->flag = TASK_RUNNING;
    task->priority = 2; /* 0.02s */
    task->level = 0;
    task_add(task);
    task_switchsub();
    load_tr(task->sel);
    task_timer = timer_alloc();
    timer_settime(task_timer, task->priority);

    idle = task_alloc();
    idle->tss.esp = memman_alloc_4k(memman, 64 * 1024) + 64 * 1024;
    idle->tss.eip = (int) &task_idle;
    idle->tss.es = 1 * 8;
    idle->tss.cs = 2 * 8;
    idle->tss.ss = 1 * 8;
    idle->tss.ds = 1 * 8;
    idle->tss.fs = 1 * 8;
    idle->tss.gs = 1 * 8;
    task_run(idle, MAX_TASKLEVELS - 1, 1);
    
    return task;
}

struct TASK *task_alloc(void)
{
    struct TASK *task;
    for (int i = 0; i < MAX_TASKS; i++)
    {
        if (taskctl->tasks[i].flag == 0)
        {
            task = &taskctl->tasks[i];
            task->flag = 1; /* using */
            task->tss.eflags = 0x00000202;
            task->tss.eax = 0;
            task->tss.ebx = 0;
            task->tss.ecx = 0;
            task->tss.edx = 0;
            task->tss.ebp = 0;
            task->tss.esi = 0;
            task->tss.edi = 0;
            task->tss.es = 0;
            task->tss.ds = 0;
            task->tss.fs = 0;
            task->tss.gs = 0;
            task->tss.iomap = 0x40000000;
            task->tss.ss0 = 0;
            return task;
        }
    }
    return 0;
}

void task_run(struct TASK *task, int level, int priority)
{
    if (level < 0)
        level = task->level;
    if (priority > 0)
        task->priority = priority;
    
    if (task->flag == TASK_RUNNING && task->level != level)
        task_remove(task);
    if (task->flag != TASK_RUNNING)
    {
        /* 唤醒 */
        task->level = level;
        task_add(task);
    }

    taskctl->lv_change = 1;
    return;
}

void task_switch(void)
{
    struct TASKLEVEL *tl = &taskctl->level[taskctl->now_lv];
    struct TASK *new_task, *now_task = tl->tasks[tl->now];
    tl->now++;
    if (tl->now == tl->running)
        tl->now = 0;
    if (taskctl->lv_change != 0)
    {
        task_switchsub();
        tl = &taskctl->level[taskctl->now_lv];
    }
    new_task = tl->tasks[tl->now];
    timer_settime(task_timer, new_task->priority);
    if (new_task != now_task)
        farjmp(0, new_task->sel);
    return;
}

void task_sleep(struct TASK *task)
{
    struct TASK *now_task;
    if (task->flag == TASK_RUNNING)
    {
        now_task = task_now();
        task_remove(task);
        if (task == now_task)
        {
            task_switchsub();
            now_task = task_now();
            farjmp(0, now_task->sel);
        }
    }
    return;
}
